1. Field of the Invention
The present invention relates to an external data read/write circuit, and more particularly to an external data read/write circuit, wherein a jack having serial clocks, serial data and bus stop lines is installed on a television which has a bus controlling system with a non-volatile memory. The present invention also relates to an external service card which is connected to the jack for writing information desired by a user into the non-volatile memory or into an integrated circuit within the television and reading out fault information of the television.
2. Description of the Prior Art
As the number of integrated circuits (ICs) employed within household electronic appliances such as televisions has increased to upgrade the appliances and to achieve more functions, a trend has developed to widely adopt a bus system (e.g., 2-wired 12C bus) for data exchange and data transmission between ICs.
Such a bus system not only allows a significant reduction of peripheral components, including a low-pass filter for a television, but also allows the manufacturing process to be automatically controlled by a computer to increase productivity.
Japanese Laid-open Publication No. 3-107283, entitled: "Portable Television with a Picture Information Display Function", discloses a technique whereby a predetermined program is stored in an IC card, and picture information of an image information circuit for generating picture information is selected to be displayed by a video signal of a television or by the program of the IC card upon pressing a selection key.
In more detail, the above Japanese Laid-open Publication No. 3-107283 includes a television circuit for receiving and demodulating a television signal, a detachable semiconductor memory device for storing a predetermined program together with a predetermined I/O terminal, and an image information circuit having a terminal which connects to the detachable memory device for generating predetermined picture information based upon the program read out from the memory device. In addition, there is provided a selection unit for selecting a television video signal of the television circuit or the picture information of the image information circuit, a display portion for displaying a picture based upon the video signal selected in the selection unit, and a stop unit interlinked with the selection unit for halting the operation of the image information circuit or television circuit. Therefore, the image information of the image information circuit that generates the picture information by the video signal of the television or program stored in the IC card, is selected to be displayed to improve the functioning of the portable television.
The above-described technique can selectively display the video signal of the television or picture information stored in the image information circuit by accommodating the program for generating the picture information of the image information circuit stored in the IC card in the television. However, data exchange and transmission between the television and external card cannot be carried out.